By MIRTA OJITO

MIAMI -- Flags are flying at half-staff here and mourners are flocking to a cemetery in Little Havana, the heart of the Cuban exile community, to grieve at the freshly dug grave of Jorge Mas Canosa, the longtime leader of the most powerful Cuban exile organization in the United States, who died here a week ago Sunday after a yearlong battle with cancer.

His death, at 58, has united foes and admirers in one thought: His passing was, they say, untimely. He died relatively young and far from reaching his goal of one day returning to a democratic Cuba, one without Fidel Castro, the revolutionary who has ruled the island for the last 38 years.

A multi-millionaire with both a common touch and the trappings of power -- including a bodyguard, a bulletproof car and a fiercely loyal retinue -- Mas never denied that one day he hoped to run for office in Cuba.

Just six months ago Mas told a reporter that he was not gravely ill and that he was going to outlive those who were spreading rumors about his impending death. But in the Mourners last week for
end, his cancer-wracked body down to less than 100 pounds and his hair all but gone, the ambitious Castro antagonist is said to have accepted his fate.

Those closest to him say this acceptance was a testament to an unshakable religious faith. But it may have also been a testament to Mas greatest asset as an astute lobbyist and political leader: his impeccable sense of timing. His political success had been so thorough, his accomplishments so great that there was little more he could do for Cuba from this side of the Florida Straits while Castro remained in power.

In his zeal to oust the Castro regime, he had masterfully exploited the power of the United States -- a country he perhaps knew more intimately than his own. In doing that, however, Mas had effectively closed off his own options. He could no longer hope to shape U.S. policy toward Cuba because he had already pretty much done so, through a series of laws that he helped to conceive, write and pass to tighten the decades-old U.S. embargo against the island.

Although Mas was by no means idle in the last month of his life, nor had his foundation lost its clout in Washington, both he and the foundation had lost the impetus that comes only when there is much work to do.

In the United States, Mas had, in effect, done everything possible until now, and done it quickly and very well. He could have lobbied for more laws to antagonize Castro, his supporters say, but it would have been difficult to top what he had already managed to accomplish.

From the moment the Cuban-American National Foundation was created in 1981, Mas showed a knack for riding the wave of America's moods. The tax-exempt foundation was the brainchild of Richard Allen, President Ronald Reagan's first national security adviser, who thought Cuban exiles could focus their influence on Cuba policy as effectively as the American Israel Political Action Committee -- Aipac -- had lobbied on behalf of Israel in Washington.

Buoyed by the euphorically anti-communist years of the Reagan administration, the foundation cemented its power by lobbying for and eventually getting Radio Marti, a United States Government radio station that broadcasts news and entertainment to Cuba. Five years later, Mas convinced Congress that a television station was also needed. TV Marti was born.

When members of Congress began talking about the need to open lines of communication with the people of Cuba, Mas stepped in, helping to shape the 1992 Cuban Democracy Act into a somewhat ambiguous law that tightens the decades-long embargo against Cuba while poking enough holes in it to allow for academic and cultural exchanges.

But perhaps Mas' greatest feat, accomplished with the help of his nemesis, Fidel Castro, was getting President Clinton to sign a bill that limited the White House's power on Cuban matters.

The Helms-Burton law was signed reluctantly by Clinton last year shortly after the Castro government shot down two unarmed planes flown by Cuban exiles. It not only prescribed U.S. penalties for foreign companies that do business with Cuba; it also put the fate of Cuba largely in the hands of Congress. It did so by shifting control of the embargo, the only weapon the United States has consistently yielded against Castro, from the president to Congress, establishing stringent conditions that must be met before it could be lifted.

Since Helms-Burton took effect, there has been very little talk in Washington about Cuba and, by definition, very little for the Cuban-American National Foundation to do while it waited for the fall or demise of Castro. When that happens, the foundation may again use its influence in Congress to define United States policy toward Cuba.

At the time of his illness, Mas had focused his energies in Europe, lobbying European leaders to pressure Castro to introduce democratic reforms in Cuba. Perhaps that route would have also taken Mas far. But, given European leaders' penchant for not siding with the United States on Cuban issues, perhaps not.

And 16 years after the formation of his foundation, while still vigorous and far from his main goal, Mas would have become, if far from powerless, a victim of his own success in the United States.